Development of porous ceramics with high strength and large surface area by spark plasma sintering

放电等离子烧结开发高强度大比表面积多孔陶瓷

• 批准号: 12650690
• 负责人: OMORI Mamoru
• 金额: $ 1.34万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650690/
• 关键词: Silicon carbide; Cubic silicon carbide; Hexagonal silicon carbide; Spark plasma sintering; Porous ceramics; Sintering; Crystal growth; セラミックス; 放電プラズマ焼結; 多孔体; ウィスカー

An electric source of spark plasma sintering (SPS) is a generator of pulsed direct current. Graphite dies are heated with this pulsed direct current, and powders in them were exposed in the electric field. Sintering of metal and ceramics powders are enhanced by effect of the electric field. Porous ceramics is used in various fields such as filters, carriers of catalysis for chemical reactors and cleaning of the exhaust gas of automobiles, and so on. The strength of porous ceramics is reduced due to pours. If the low strength is improved, the porous ceramics should be used in new fields.There are cubic and hexagonal crystals of commercially available SiC powders, β-SiC and α-SiC. These two powders were sintered between 1600 ℃ and 2200 ℃ by SPS in a vacuum. The crystal structure of the β-SiC powder was transformed to α-SiC stable at high temperature. The texture of the compact sintered from the β-SiC powder was composed of connected long crystals and contained 30 % pores. There was no grain boundary between the connected crystals ; that is called a porous single crystal. α-SiC crystals included in the β-SiC crystal grew and connected with other crystals with right crystal axes. The density did not increase with increasing heating temperatures, and the porous ceramics was stable at high temperatures. The compact sintered from the α-SiC powder had a many grain boundaries, and its densification was conducted by sintering mechanism and progressed gradually by heating. The α-SiC compact was not sable at high temperatures. The strength of the β-SiC compact was 141MPa and one seventh as large as that of a dense SiC body.It is concluded that a porous SiC ceramics with the high strength and large surface area is fabricated from the β-SiC powder by SPS.

放电等离子烧结(SPS)电源是脉冲直流电源。用这种脉冲直流电流加热石墨模具，使其中的粉末暴露在电场中。电场的作用促进了金属和陶瓷粉末的烧结。多孔陶瓷在过滤器、化学反应器催化剂载体、汽车尾气净化等领域有着广泛的应用。浇注会降低多孔陶瓷的强度。如果要改善材料的低强度，多孔陶瓷应该在新的领域中得到应用。市售的碳化硅粉末有立方晶和六方晶两种，β-碳化硅和α-碳化硅。这两种粉末在1600~2200℃范围内真空烧结。β-碳化硅粉末的晶体结构在高温下向稳定的α-碳化硅转变。由β-SiC粉末烧结的压坯织构由连通的长晶组成，并含有30%的气孔。相连的晶体之间没有晶界，这就是所谓的多孔单晶。α-碳化硅晶体中的β-碳化硅晶体生长，并以正确的晶轴与其他晶体相连。多孔陶瓷的密度不随加热温度的升高而增加，在高温下是稳定的。由α-SiC粉末烧结的压坯具有多个晶界，其致密化是通过烧结机制进行的，并通过加热逐步进行。α-碳化硅压坯在高温下不能硫化。β-SiC体的强度为141 Mpa，是致密的SiC体的七分之一，说明以β-SiC粉为原料，可以制备出强度高、比表面积大的多孔碳化硅陶瓷。